The present invention relates to an improved surgical device for single-handed insertion of various styles of foldable, intraocular lenses. The invention is a reusable device for compressing various styles of foldable, intraocular lenses; injecting these compressed lenses into patients' eyes in a controlled, single-handed fashion through extremely small incisions; and manipulating the lenses following injection. The invention is particularly useful in inserting acrylic-based lenses.
Many surgical procedures and devices have been developed during the fairly short history of cataract surgery. Prior to the introduction of foldable lenses, the state of the art of cataract lens replacement was performed by manual extracapsular cataract extraction ("ECCE") and insertion of a rigid intraocular lens through a corneal or sclerocomeal incision that was typically 6.5 to 8.0 mm in length, or longer. The size of the wound created by such an incision typically required suturing. Patients who have undergone this form of cataract surgery experience complications such as endothelial cell loss, wound instability, postsurgical intraocular pressure rise, surgically induced astigmatism, and poor visual acuity during the postoperative period. The undesirable effects of ECCE and rigid lens implantation are largely attributable to wound size.
Since their introduction, elastic or "foldable," artificial lenses have become the replacement lens of preference for many cataract patients, particularly those undergoing phacoemulsification. Such a lens can be compressed and therefore occupies a smaller cross-sectional area than a rigid intraocular lens. Consequently, a foldable intraocular lens can be inserted through a smaller incision than a rigid lens. Implanting foldable lenses in this manner decreases wound size and contributes to earlier and better visual rehabilitation than large-incision surgery. Through phacoemulsification and injection of foldable intraocular lenses, the size of corneal and sclerocomeal incisions can be reduced by half or more. Instead of corneal or sclerocomeal incisions greater than 6.5 mm, cataract can be removed and intraocular lenses can be inserted through incisions of approximately 3.2 mm down to even 3.0 mm.
Although commercially available in several styles, foldable intraocular lenses generally share several characteristics. Foldable intraocular lenses are typically fabricated of materials that provide optical strength comparable to the natural lenses they replace, are chemically and biologically inert, and demonstrate durability characteristics that are necessary for articles permanently implanted in vivo. In addition, foldable intraocular lenses are elastic, capable of being compressed, passed through small incisions into the eye, and have resilience adequate to allow them to return to their intended shape following compression. The greater the resilience of a lens, the greater it can be compressed without permanent deformation, thereby allowing it to be inserted through relatively smaller incisions. Foldable intraocular lenses have traditionally been made of polymeric material such as silicone or polymethylmethacrylate ("PMMA"), but more recently, acrylic-based foldable intraocular lenses have become available.
Acrylic-based intraocular lenses are related to the PMMA rigid lenses in optical quality and chemistry. However, the nature of the material composition of acrylic-based lenses causes them to unfold slowly in the eye following insertion. This gives the surgeon much greater control during a most critical party of the surgery: insertion and manipulation of the lens within the capsular bag. Acrylic-based lenses have a "sticky" characteristic that causes adhesion of the lens to forceps, delaying the release of the lens into the capsular bag. Acrylic-based lenses are more fragile than silicone elastomer lenses. This can be demonstrated by examining lenses under a microscope after they have been grasped with forceps. Lens folding techniques that utilize forceps increase the risk of inducing lens surface defects and causing longitudinal cracks from taco-type folds. This is particularly true for those lenses that are of more fragile material composition than others, such as acrylic-based lenses. Consequently, there is a need for an inserter that can reduce the occurrence of surface scratches on fragile lens surfaces. Additionally, there is a need for an inserter that reduces the occurrence of central longitudinal cracks caused by taco-type folds.
In addition to material composition, foldable lenses differ structurally in the manner in which they are designed to be attached within the eye. There are three styles of lenses: one-piece, three-piece and hybrid lenses. A one-piece lens is manufactured entirely of optical quality material, with a refractive portion mounted in the center of an ovoid-rectangular plate that contains opposing fenestrations for attachment of the lens to the eye. Examples of one-piece lenses are the STAAR ELASTIC lens, model AA-4203VF and the STAAR TORIC lens, model AA-4203TF, both available from STAAR Surgical Company, Monrovia, Calif. U.S.A. Since one-piece lenses include integrated eye attachment points, one-piece lenses must be large enough to effectively fit the capsular bag of the eye.
Another style of intraocular lens is the three-piece lens. A three-piece lens is comprised of a central refractive portion made of optical quality material having, typically, two (2) haptics attached to its perimeter at opposite poles. The haptics are usually made of a shape-memory polymer, and are formed into a "C " or "J" shape. Examples of three-piece lenses are the STAAR ELASTIMIDE lens, mode AQ-1016V and the STAAR ELASTIMIDE lens, model AQ-2003V, both available from the STAAR Surgical Company, Monrovia, Calif. U.S.A.
A hybrid lens is also available. The hybrid lens combines the single-material construction of the one-piece lenses with the haptics found in three-piece lenses. Hybrid lenses are manufactured entirely of optical quality material, however, unlike one-piece lenses, they have a clearly defined central refractive portion from which haptics extend. Unlike three-piece lenses, the haptics of hybrid lenses are made of the same optical quality material as the plate of the one-piece lenses.
Lens selection is made by the surgeon based on the surgeon's personal preferences and the needs of a particular patient. Unfortunately, because many of the lens insertion tools presently on the market are designed for the insertion of only a particular size or style of lens, the choice of lens to be inserted often dictates the lens insertion tool used by the practitioner. Insertion devices for foldable intraocular lenses typically fall into three categories: forceps-type devices, screw-type devices and plunging-type devices. Forceps-type devices use opposable members to compress a foldable lens and insert the compressed lens through an incision in the eye. Screw-type and injector-type devices compress a foldable lens and then force it through a tube that has been placed in an incision in the eye. It is generally appreciated in the art that screw-type and injector-type devices provide an increased measure of compression and control over forceps-type devices and thereby reduce incision tearing while at the same time allowing for in vivo manipulation of the foldable lens.
Of the lens inserters presently available, the screw-type are most commonly used by practitioners. A screw-type inserter acts to compress and inject a lens by advancing a threaded plunger through a threaded tube. Examples of screw-type inserters are shown in Brady et al. U.S. Pat. Nos. 5,582,613, Patton et al. 4,834,094, Patton et al. 4,836,201, Kammann et al. 5,354,333, Blake 5,468,246, Orchowski et al. 5,474,562 and Feingold 5,582,614. Screw-type inserters are driven either electrically or manually. Electrically driven injectors are comprised of motors and gearings that are attendant to similar medical appliances. Such devices must be electrically isolated from the patient, must be specially designed to be sterilized, and by the nature of motor placement, typically have a large moment of inertia at the end of the device distal from the patient. This reduces the facility by which such devices may manipulate lenses following insertion. On the other hand, a manually actuated screw-type inserter requires a surgeon to provide both rotational actuation to the screw portion of the device and opposing resistance on the tube portion of the device to advance the screw within the tube and insert the lens into a patient's eye. Therefore, manually actuated screwtype injectors are, by the physics of their construction, two-handed devices.
Certain manually-actuated, plunging-type intraocular lens injectors are found in the prior art, and have been used to push compressed intraocular lenses through insertion tubes into patients' eyes. However, the unique challenges and physics associated with the eye place difficult demands on the devices and techniques employed by a surgeon performing ophthalmic surgery. As a result, the present state of the art should be improved to meet these demands and challenges.
Specifically, predictability in technique and device operation, even with the use of different sizes or styles of intraocular lenses, as well as affordability, is important to a successful surgical outcome. Consequently, there is a need for lens insertion devices that are reusable, easily sterilized, and cross-compatible with various types and styles of intraocular lenses, particularly acrylic-based lenses. Tactile and visual feedback is critical to an improved lens insertion device, as is ease of manipulation of the intraocular lens following its insertion into the eye. Therefore, there is a need for lens insertion devices that are lightweight and well balanced, that provide good hand control, that have a window so that the compression of lenses can be verified, that are constructed to certain tolerances to provide tactile feedback, and that have specially designed tips for maneuvering lenses following their insertion. Furthermore, there is a need for lens insertion devices that limit the insertion of foreign fluid, including air, into the eye. Importantly, there is also a need for a device that inserts an intraocular lens with a single-hand.